I had a 2009 BR Subaru Liberty (Legacy) with a Check Engine Light (CEL) illuminated. The OBD2 scanner showed DTC P0031: Bank 1, sensor 1, heater circuit voltage low.
This video shows how to use an ohmmeter to manually test the continuity of the oxygen sensor, and the location of the pre and post-cat oxygen sensors.
Enjoy!
Paul.
![](https://i.ytimg.com/vi/72_UlYb9HMw/maxresdefault.jpg)